How badly spam links can affect a site?

I had started a forum about 2 weeks ago. Due to inadequacies of vBullein (I had used vBulletin as the forum software), I was not able to easily find ways to set the registration such that it would require email verification, and also to disallow new users from posting links.

The forum was easily on number 2 spot on both Yahoo and Bing for a specific phrase that I was targeting. Then an spammer from Canada had posted 15 messages with links to all kind of porn sites. I of course deleted the messages in the morning right away. But my site had also completely vanished from Bing and Yahoo, just after one night.

I've heard that search engines just do this as a warning to the Web master. Now, my questions are:

1. Has anyone had this experience before? I mean this is really harsh than only just cause someone posted links overnight, the site completely vanishes from search engines.

2. Can you post some links that references this issue and a possible solution to getting the old ranking back.

Jordan02 - Matt Cutts - Google's head engineer that fights web spam, just put a Google webmaster central video on YouTube that talks about how/when to get reconsidered.
Take a look at it and let us know

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